The common theme of the work is the assessment of differentiation of properties among different excitable tissues in different animals, in different stages of development and different genetic mutants of the same animal. The following specific projects are proposed. 1) Analysis of Ca-dependent action potential The ion selectivity and kinetics of the Ca channel will be analyzed using voltage clamp techniques on the internally dialyzed nerve cell soma of the fresh water snail, limnea stagnalis. The analysis will be extended to vertebrate nerve cells such as spinal ganglion cells of the rat. 2) The gating mechanism of the membrane channel during the anomalous rectification will be studied in the starfish egg cell as well as in frog skeletal muscle fibers. 3) Electrophysiology and the role of Ca in early development. The membrane properties of egg cells of the coelenterate Renilla will be analyzed in relation to development. The ionic mechanism of the activation potential will be studied in eggs of the echiuran, Urechis caupo, using voltage clamp techniques.